Trying to get my car dialed in after my carb swap, having a sligh hesitation when getting on the gas off idle and when stomped on. There is no backfiring at all, just a little stumble then it goes. I checked to make sure the accellerator pump activates right when the throttle opens, and it does. I've confirmed the float levels are ok. Fuel pressure is 6psi. Vacuum is a steady 16". Timing is set to 12 initial. Plugs, wires, cap and rotor are new. I'm running a Holley 750 VS (3310) with 66 primary jets. The pump cam is set at the "1" position and the cam is green in color. I pulled the discharge nozzle tonight and it is a 28 one. I was thinking of trying a larger shooter to see if that fixes the issue. Is there anything else I should consider that might fix the problem?

Also what is the difference between a "tube" and "straight" nozzle? Is one better than the other?

Thanks in advance

Kevin

 

Tube squirters direct the shot into the booster venturi. Straight just dumps it in the airstream. The tube type should distribute the fuel a little more evenly in the airstream, theoretically.

You may have a powervalve that is too low a number (manifold vacuum has to drop too much in order to start opening the PV). The carb probably came with a 6.5 PV, you might try a 7.5 if a .031 squirter doesn't solve the problem.

 

I had the same problem. I stepped all the way up to a 48 squirter and still had a little stumble.

I sent the main body out to the carb shop in california and they installed downleg single stepped boosters in my primaries and that fixed the problem. My 305 wasn't drawiing hard enough on my holley 670 to pull enough fuel into the airstream at low rpm but the more aggressive booster design fixed the problem. You con do a search under my user name for more details. Good luck.